Pressurized Gas Release Mechanism

ABSTRACT

A gas seal for containing a pressurized fluid in a container. The gas seal includes a rupturable portion having a stress riser formed therein, and an extension coupled to the rupturable portion proximate the stress riser such that a predetermined minimum force applied to the extension is transferred to the stress riser to produce a rupture of the rupturable portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of, U.S. application Ser. No. 12/321,537 (filed on Jan. 22, 2009), which claims the benefit of U.S. Provisional Patent Application Ser. Nos. 61/063,034 (filed on Jan. 31, 2008), 61/062,460 (filed on Jan. 25, 2008), and 61/011,961 (filed on Jan. 22, 2008).

BACKGROUND OF THE INVENTION

The present invention relates to devices used to activate gas-actuatable elements in a vehicle occupant protection system and, more particularly, to a mechanism for releasably containing a pressurized inflation fluid in a container used in a stored gas inflator or hybrid gas generating system.

Inflation systems for deploying inflatable devices such as air bags in motor vehicles generally employ an inflator or gas generating system in fluid communication with an uninflated air bag. The inflator is typically triggered by a firing circuit when a sensor determines that vehicle acceleration has exceeded a predetermined threshold value (for example, through the use of an acceleration-responsive inertial switch.)

Air bag inflation systems often utilize a stored gas generator (or hybrid gas generator) housed within the B-pillar of a car, for example. Stored gas generators contain pressurized gas that is released to inflate the airbag upon receipt of a predetermined signal from the sensor. An ongoing challenge is to reduce the time required to release the stored gas upon a crash event. Furthermore, improved safety and reduced manufacturing costs are also ongoing concerns. Improvements in any of these areas would provide an advantage over state-of-the-art gas release systems.

SUMMARY OF THE INVENTION

In one aspect of the embodiments of the present invention, a gas seal is provided for containing a pressurized fluid in a container. The gas seal includes a rupturable portion having a stress riser formed therein, and an extension coupled to the rupturable portion proximate the stress riser such that a predetermined minimum force applied to the extension is transferred to the stress riser to produce a rupture of the rupturable portion.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings illustrating embodiments of the present invention:

FIG. 1A is an end view of a gas seal for sealing a gas-storage bottle in accordance with a first embodiment of the present invention.

FIG. 1B is a cross-sectional view of the gas seal shown in FIG. 1A.

FIG. 2A is an end view of a gas seal for sealing a gas-storage bottle in accordance with a second embodiment of the present invention.

FIG. 2B is a cross-sectional view of the gas seal shown in FIG. 2A.

FIG. 3A is an end view of a gas seal for sealing a gas-storage bottle in accordance with a third embodiment of the present invention.

FIG. 3B is a cross-sectional view of the gas seal shown in FIG. 3A.

FIG. 4A is an end view of a gas seal for sealing a gas-storage bottle in accordance with a fourth embodiment of the present invention.

FIG. 4B is a cross-sectional view of the gas seal shown in FIG. 4A.

FIG. 5 is a cross-sectional view of the gas seal shown in FIG. 1 incorporated into a housing attached to a gas bottle.

FIG. 6 is a cross-sectional view of the assembly shown in FIG. 5 including a diffuser coupled to the housing.

FIG. 7 is a partial cross-sectional view of the assembly shown in FIG. 6 during the first stage of breakage of the gas seal.

FIG. 8 is the partial cross-sectional view of FIG. 7 after breakage of the gas seal.

FIG. 9 is a cross-sectional view of a gas seal for sealing a gas-storage bottle in accordance with another embodiment of the present invention.

FIG. 10 is a cross-sectional view of the gas seal shown in FIG. 9 incorporated into a housing attached to a gas bottle.

FIG. 11 is a partial cross-sectional view of a gas seal in accordance with another embodiment of the present invention incorporated into a housing attached to a gas bottle.

FIG. 12 is a partial cross-sectional view of a gas seal in accordance with another embodiment of the present invention incorporated into a housing attached to a gas bottle.

FIG. 13 is a partial cross-sectional view of the gas seal shown in FIG. 10 after activation of the igniter and immediately prior to breakage of the gas seal.

FIG. 14 is the cross-sectional view of FIG. 10 after breakage of the gas seal and detachment of a portion of the gas seal.

FIG. 15A is an end view of a portion of a gas seal for sealing a gas-storage bottle in accordance another embodiment of the present invention.

FIG. 15B is a cross-sectional view of the portion of the gas seal shown in FIG. 15A.

FIGS. 16-18 are cross-sectional views of gas seals for sealing a gas-storage bottle in accordance with other alternative embodiments of the present invention.

FIG. 19 is a cross-sectional view of the gas seal shown in FIG. 16 incorporated into a housing attached to a gas bottle.

FIG. 20 is a partial cross-sectional view of the gas seal shown FIG. 16 incorporating an additional sealing element.

FIG. 21 is a partial cross-sectional view of a gas seal for sealing a gas-storage bottle in accordance with another alternative embodiment of the present invention.

FIG. 22 is a partial cross-sectional view of the gas seal shown in FIG. 21 after activation of the igniter and immediately prior to breakage of the gas seal.

FIG. 23 is the partial cross-sectional view of FIG. 22 after breakage of the gas seal.

FIG. 24 is a schematic view of an airbag system and a vehicle occupant protection system incorporating an inflator including a gas seal in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Similar reference characters denote similar features consistently throughout the attached drawings.

FIGS. 1-8 show various embodiments of a mechanism 10 for releasably containing pressurized fluid in a container, in accordance with the present invention. Referring in particular to FIGS. 6-8, mechanism 10 is shown secured to a gas bottle or tank 18 in which a pressurized fluid (in this case, an inflation gas) is stored. Bottle 18 has an annular wall 36 defining an opening 24, with an annular shoulder 37 formed in wall 36 and an annular ledge 26 extending along a base portion of shoulder 37.

Referring to FIGS. 1A, 1B, 5, and 6, in one embodiment, mechanism 10 includes a gas seal 21 comprising a rupturable portion 22 secured in fluid communication with an interior of bottle 18. Rupturable portion 22 forms a fluid-tight barrier preventing flow of pressurized gas through or around the member. Rupturable portion 22 may be seated along gas bottle annular ledge 26 and welded or otherwise secured thereon to obstruct flow of the pressurized fluid during normal vehicular operation. Alternatively, as shown in FIGS. 5 and 6, the rupturable portion may be seated along an edge of a housing 12 which is attached to an opening of bottle 18. Rupturable portion 22 also has at least one stress riser 22 a coined, embossed, or otherwise formed along one or more sides thereof. Stress riser 22 a defines a region along which the rupturable portion fractures to release the pressurized fluid from the bottle, when the rupturable portion is stressed as described below.

In the embodiments shown in FIGS. 1A-4B, the stress riser comprises a continuous groove (shown as 22 a, 122 a, 222 a, 322 a) extending along a respective first surface 22 c, 122 c, 222 c, 322 c of the corresponding one of rupturable portions 22, 122, 222, 322. However, the stress riser may reside in an interior portion of the rupturable portion, rather than on an outer surface of the part. In another embodiment (not shown), rather than a single stress riser, a plurality of stress risers are formed on or in the rupturable portion.

Referring again to FIGS. 1A, 1B, 5, and 6, in one embodiment, member 22 is a disk stamped, molded, or otherwise formed from a metallic, polymeric, or other material into which stress riser 22 a may be formed and which possesses the strength necessary to resist the forces exerted on the member by the compressed gas stored in bottle 18. The materials and structural details of the member will depend on such factors as the pressure of the gas sealed in bottle 12 and the desired performance characteristics of an inflator 8 or gas generating system into which mechanism 10 is incorporated. For example, members made from materials and/or having structures which are more or less readily ruptured may be used.

A rigid, cantilevered member or extension 23 is coupled to the rupturable portion using any suitable method. In the embodiment shown in FIGS. 1A-1B, extension 23 is coupled to rupturable portion 22 using any suitable method. Extension 23 is shown attached to a surface 22 d of rupturable portion 22 opposite surface 22 c. In the embodiment shown in FIGS. 1A-1B, the extension has a maximum cross-sectional dimension “D” (viewed looking into the page in FIG. 1A) generally coincident with a perimeter defined by the “deepest” portion 22 b of groove 22 a, which defines the region of minimum material thickness along the rupturable portion 22. This helps to ensure optimum transfer of force from the extension to the stress riser, which aids in ensuring that a predetermined minimum force acting on the extension produces a rupture of the rupturable portion. This, in turn, permits pressurized inflation fluid flow past the gas seal.

As seen in the embodiments shown in FIGS. 1A-4B, the extension can be solid or tubular or otherwise hollow. The extension can be formed from a metallic material, a polymeric material, or any other material having rigidity suitable for the purposes described herein. The extension can have any desired shape and may be attached to the rupturable portion so as to extend from the rupturable portion at any desired angle with respect to the rupturable portion surface. In a particular embodiment (shown in FIGS. 1A and 1B), the extension is cylindrical and is extends perpendicular to a surface of the rupturable portion. The extension may be attached to the rupturable portion by any of a variety of known methods, such as welding or adhesives. As seen in FIGS. 5 and 6, rupturable portion 22 is attached and sealed to the gas bottle or housing such that extension 23 resides exterior of the gas bottle 18

FIGS. 2A and 2B show a gas seal in accordance with another embodiment of the present invention, similar to the embodiment shown in FIGS. 1A-1B. In FIGS. 2A and 2B, extension 123 is a solid structure attached to rupturable portion 123.

In another embodiment (seen in FIGS. 3A-3B), the gas seal comprises a rupturable portion 222 having an extension 223 formed integrally therewith. As in the previously described embodiments rupturable portion 222 has a stress riser 222 a coined, embossed, or otherwise formed on one or both sides thereof. Extension 223 is formed from a solid slug of steel or other suitable material. Typical methods of manufacture of the slug include forging, cold heading and impacting, although other alternative methods may be used. A configuration designed to reduce the mass of the extension is shown in FIGS. 4A & 4B, wherein the extension 323 is hollow.

Although the embodiments shown in FIGS. 6-8 include the embodiment of the gas seal shown in FIGS. 1A-1B for purposes of the following explanation, it will be understood that any of the gas seal embodiments shown in FIGS. 2A-4B may alternatively be used in the mechanism. Referring to FIG. 6, a device capable of supplying a predetermined minimum force on demand to the extension 23 is mounted or coupled to mechanism 10 so as to permit fluid communication between the device and the extension upon activation of the inflator or gas generating system. Suitable force-generating devices include explosively actuated projectiles or pin pokers (which directly contact the extension when activated), and any devices capable of supplying a gas jet or shock front, for example initiators, gas generators and detonators. In the embodiment shown in FIGS. 6-8, a known initiator 66 is crimped or otherwise suitably secured to a periphery of housing 12 and extends through a wall of the housing so that, upon activation of the initiator 66, fluid communication between extension 23 and the initiator is enabled. One exemplary initiator construction is described in U.S. Pat. No. 6,009,809, herein incorporated by reference.

In addition, it may be seen from FIG. 6 that rupturable portion 22 and extension 23 lay along a common axis L extending between a first end 14 of housing 12 and a second end 16 of housing 12. It may also be seen that initiator 66 is spaced apart from axis L. Stated another way, initiator 66 does not intersect axis L along which member 22 and extension 23 are positioned. As used herein, the term “axis” is understood to designate a line in relation to which parts of a structure or body may be referenced. It may also be seen that initiator 66 is positioned so as to directly apply a lateral load (i.e., a load or force acting laterally or transversely to axis L) to extension 23. However, the force may alternatively be applied indirectly, depending on the requirements of a particular application.

Referring to FIGS. 6-8, a hollow diffuser 44 is machined or otherwise formed from steel or other suitable materials, and then welded or otherwise fixed to housing second end 16. Diffuser 44 may alternatively be formed integral with housing 12. Diffuser 44 functions to distribute gas flowing through and received from housing 12. A plurality of gas discharge orifices 54 is spaced about a circumference of the diffuser. The embodiment shown in FIGS. 6-8 includes four gas discharge orifices 54 evenly spaced about the circumference of the diffuser. The diffuser may incorporate a filter (not shown) therein to filter combustion products or other debris from the inflation fluid prior to gas distribution. Any suitable metallic mesh filter, woven wire cloth, or other type of filter may be used, many examples of which are known and obtainable from commercially available sources (for example, Wayne Wire Cloth Products, Inc. of Bloomfield Hills, Mich.)

Operation of the mechanism will now be discussed with reference to FIGS. 6-8. Upon occurrence of a crash event, the igniter 66 is activated by a signal received from a crash sensor or accelerometer (not shown). Pressure generated by activation of the initiator acts on extension 23 applying a predetermined minimum force to the extension.

With the stored pressurized fluid acting on rupturable portion 22, the rupturable portion is stressed. This applied stress is less than the break strength of the rupturable portion along stress riser 22 a. When the predetermined minimum force is applied to the extension attached to the rupturable portion, a corresponding reaction stress is applied at the junction between the rupturable portion and the extension. This stress induces an additional tensile stress in the rupturable portion. This additional tensile stress, combined with the stress on the rupturable portion due to the pressure from gases stored in the bottle, exceeds the break strength of the rupturable portion along the stress riser. The rupturable portion fractures along the stress riser, and the fracture propagates along the stress riser. The center portion of the rupturable portion breaks free, with the extension attached, and is pushed away from the gas bottle by the contained gas pressure.

Stored pressurized fluid within bottle 18 then flows through rupturable portion 22 and through housing 12, into diffuser 44, and out of the diffuser through orifices 54 and into an airbag or other inflatable element (not shown). A filter (not shown) positioned in diffuser 44 traps by-products of initiator activation, portions of the member, or other debris within the diffuser to prevent their entry into the airbag.

The thickness of the rupturable portion along the stress riser affects the pressure at which the rupturable portion will burst. The burst strength of the rupturable portion is greater than the stress induced by the compressed gas alone, but less than the combined stress resulting from the compressed gas and the stresses due to the force moment resulting from side loading of the cantilevered extension. The burst strength of the member is also less than the pressure needed to rupture the bottle internally. This provides a safe gas relief mechanism for over-pressurization situations caused by, for example, afire external to the gas bottle.

FIGS. 9-14 show various alternative embodiments of mechanism 110 for releasably containing pressurized fluid in a container, in accordance with the present invention.

Referring to FIGS. 10-14, mechanism 110 is shown secured to a gas bottle or tank 18 in which a pressurized fluid (in this case, an inflation gas) is stored. Bottle 18 has an annular wall 36 defining an opening, with an annular shoulder 37 extending from annular wall 36 and an annular ledge 26 extending along a base portion of shoulder 37.

Referring to FIGS. 9-14, mechanism 110 includes a gas seal 421 comprising a rupturable portion 422 secured in fluid communication with an interior of bottle 18. Rupturable portion 422 forms a fluid-tight barrier preventing flow of pressurized gas through or around the rupturable portion. Rupturable portion 422 may be seated along gas bottle annular ledge 26 and welded or otherwise secured thereon to obstruct flow of the pressurized fluid during normal vehicular operation. Alternatively, as shown in FIGS. 10-14, the rupturable portion may be seated along an edge of a housing 12 which is attached to an opening of bottle 18.

In the embodiments shown in FIGS. 9-14, rupturable portion 422 comprises an upper portion 422in of a drawn cup including a flange 422 a. An extension 422 n is coupled to upper portion 422 m so as to enable breakage of the connection between the upper portion and extension upon application of a predetermined minimum force to a portion of the gas seal. Also, a projection extends from the extension 422 n against which the predetermined minimum force acts to produce rupture of the rupturable portion. In the embodiments shown in FIGS. 9-14A, the projection is in the form of a seal portion 423 welded or otherwise attached to the closed end of the cup. Gas seal 421 includes relatively thicker wall sections 422 c and 422 d, and at least one relatively thinner wall section 422 e interposed between thicker wall sections 422 c and 422 d. As wall section 422 e is relatively thinner, this section is less resistant to stresses applied to rupturable portion 422. Thus, the gas seal will tend to break along this relatively thinner wall section before breaking along other portions of the seal. Therefore, this thinner wall section 422 e defines a circumferential break region along which the rupturable portion 422 fractures to release the pressurized fluid from the bottle when the rupturable portion is stressed as described below.

The thickness of thinner wall section 422 e controls the burst strength of the cup. The thinned section thickness is specified such that the breaking strength of the cup along the break region is greater than the stress induced in the cup wall by the gas pressure contained in the bottle. The seal portion 423 attached to the cup 422 acts as a gas seal between the housing bore and the cup. As seen in FIG. 11, various alternative seal portion configurations may be employed to improve the gas seal and reduce the impact of component tolerances on the gas seal. For example, in the embodiment shown in FIG. 11, flaps 423 a′ resiliently deflect toward axis L′ when seal portion 423′ is inserted into housing passage 12 a, thereby forming a seal between the seal portion and a wall of passage 12 a. In addition, a separate seal (such as an (O-ring 499) (FIG. 12) may be included to improve the gas seal.

The materials and structural details of the rupturable portion will depend on such factors as the pressure of the gas sealed in bottle 12 and the desired performance characteristics of an inflator 8 or gas generating system (see FIG. 10) into which mechanism 110 is incorporated. For example, members made from materials and/or having structures which are more or less readily ruptured may be used.

A device capable of generating a predetermined minimum force within housing 12 is mounted so as to permit fluid communication with the cup upon activation of the inflator or gas generating system. Suitable force-generating devices include explosively actuated projectiles or pin pokers, and any devices capable of supplying a gas jet or shock front, for example initiators, gas generators and detonators. In the embodiments shown in FIGS. 10-14, a known initiator 66 is crimped or otherwise suitably secured to a periphery of housing 12 and extends through a wall of the housing so that, upon activation of the initiator 66, fluid communication between gas seal 21 and the initiator is enabled. One exemplary initiator construction is described in U.S. Pat. No. 6,009,809, herein incorporated by reference.

In addition, it may be seen from FIGS. 9 and 10 that cup 422 and seal portion 423 lay along a common axis L′ extending between a first end 14 of housing 12 and a second end 16 of housing 12. It may also be seen that initiator 66 is spaced apart from axis L′. Stated another way, initiator 66 does not intersect axis L′ along which cup 422 and disk 423 are positioned.

Referring to FIGS. 10 and 14, a hollow diffuser 44 (as seen in the embodiments disclosed in FIGS. 1-8) is machined or otherwise formed from steel or other suitable materials, and then welded or otherwise fixed to housing second end 16.

Operation of the embodiments shown in FIGS. 10-16 is as follows. Referring to FIGS. 13 and 14, upon occurrence of a crash event, the igniter 66 is activated by a signal received from a crash sensor or accelerometer (not shown). When the igniter is fired, a cavity bounded by the cup flange 422 a, the seal portion 423, the cup walls 422 c, 422 d, and 422 e and the housing bore is pressurized. Pressure generated by activation of the initiator acts on cup 422 and seal portion 423, applying a load on seal portion 423 in the direction of arrow A (substantially parallel with axis L′) (FIG. 13). This force induces an axial tensile load in the cup wall. The combination of the stress induced by the bottle gas pressure and the stress induced by the load on the seal portion exceeds the break strength of the relatively thinner portion 422 e of the cup wall. The cup fractures along the thinner wall section 422 e. The end of the cup and attached disk 423 are pushed down the housing bore by the gas pressure in the bottle, thereby releasing the gas from the bottle.

Stored pressurized fluid within bottle 18 then flows through rupturable portion 22 and through housing 12, into diffuser 44, and out of the diffuser through orifices 54 and into an airbag or other inflatable element (not shown). A filter (not shown) positioned in diffuser 44 traps by-products of initiator activation, portions of the member, or other debris within the diffuser to prevent their entry into the airbag.

The wall thickness of the thin-walled portion 422 e of the cup affects the pressure at which the rupturable member will burst. The burst strength of the rupturable portion is greater than the stress induced by the compressed gas in the bottle, but less than the combined stress produced by the compressed gas and the forces on the cup resulting from activation of the igniter. The breaking strength of the rupturable portion is also less than the pressure inside the bottle needed to rupture the bottle. This provides a safe gas relief mechanism for over-pressurization situations caused by, for example, a fire external to the gas bottle.

FIGS. 15A-23 show other various embodiments of a mechanism 210 for releasably containing pressurized fluid in a container, in accordance with the present invention. Referring in particular to FIGS. 15A-16 and 20, in one embodiment, mechanism 210 includes a gas seal 521 comprising a rupturable portion 522 secured in fluid communication with an interior of a bottle 18 as previously described. Rupturable portion 522 forms a fluid-tight barrier preventing flow of pressurized gas through or around the member. Rupturable portion 522 may be seated along gas bottle annular ledge 26 and welded or otherwise secured thereon to obstruct flow of the pressurized fluid during normal vehicular operation. Alternatively, as shown in FIGS. 19-22, the member may be seated along an edge of a housing 12 which is attached to an opening of bottle 18. Rupturable portion 522 also has a stress riser 522 a coined, embossed, or otherwise formed along one or both sides thereof. Stress riser 522 a defines a region along which the rupturable portion fractures to release the pressurized fluid from the bottle, when the rupturable portion is stressed as described below.

In the embodiments shown in FIGS. 15A-18, the stress riser comprises a continuous groove (shown as 522 a, 622 a, 722 a) extending along a respective first surface 522 c, 622 c, 722 c of corresponding ones of rupturable portions 522, 622, 722. However, the stress riser may reside in an interior portion of the rupturable portion, rather than on an outer surface of the part. In another embodiment (not shown), rat her than a single stress riser, a plurality of stress risers are formed in the rupturable portion.

In the embodiment shown in FIGS. 15A-15B, the rupturable portion 522 is a disk stamped, molded, or otherwise formed from a metallic, polymeric, or other material into which stress riser 522 a may be formed and which possesses the strength necessary to resist the forces exerted on the member by the compressed gas stored in bottle 18. Rupturable portions 622 and 722 have structures similar to rupturable portion 522. The materials and structural details of the member will depend on such factors as the pressure of the gas sealed in bottle 12 and the desired performance characteristics of an inflator 8 (see FIG. 19) or gas generating system into which mechanism 210 is incorporated. For example, members made from materials and/or having structures which are more or less readily ruptured may be used.

In the embodiments shown in FIGS. 16-18, each of gas seals 521, 621, and 721 also includes respective a extension 523, 623, 723 coupled to their respective rupturable portions using any suitable method. The extensions 523, 623, 723 can be solid or tubular or otherwise hollow. The extensions 523, 623, 723 can be formed from a metallic material, a polymeric material, or any other material having rigidity suitable for the purposes described herein. The extensions can have any desired shape and may be attached to their respective rupturable portions so as to extend from the rupturable portion at any desired angle with respect to the rupturable portion surface. In particular embodiments (shown in FIGS. 15A-22), the extension is cylindrical and is extends perpendicular to a surface of the respective rupturable portion. The extensions are attached to the respective rupturable portions using any of a variety of known methods, such as welding or adhesives. As seen in FIGS. 19-21, rupturable portion 522 (and also the other rupturable portions 622, 722) is attached and sealed to the gas bottle or housing such that extension 523 resides exterior of the bottle. As seen in the embodiments shown in FIGS. 16-18, the extensions also have corresponding flanges 523 a, 623 a, and 723 a, 823 a formed or attached to ends of the extensions. The flange attached to the extension acts as a gas seal between the housing bore and the extension. As seen in FIGS. 16-18 and 20-21, various alternative flange configurations may be employed to improve the gas seal and reduce the impact of component tolerances on the gas seal. In addition, separate seal (such as an O-ring 100) (FIG. 20) may be included to improve the gas seal. In another embodiment (seen in FIG. 17), extension 623 is formed from a solid slug of steel or other suitable material. Typical methods of manufacture of the slug include forging, cold heading and impacting, although other alternative methods may be used.

Referring to FIGS. 19-22, a device (for example, an initiator 66) capable of generating a pressure surge within housing 12 is positioned along the length of the extension so as to permit fluid communication with the extension upon activation of the inflator, as previously described.

Referring to FIG. 19, a hollow diffuser 44 is machined or otherwise formed from steel or other suitable materials, and then welded or otherwise fixed to housing second end 16 as previously described.

The stress risers 522 a, 622 a, 722 a, 822 a on respective rupturable portions 522, 622, 722, 822 provide circumferential break regions. The thickness of the rupturable portions along these stress risers controls the breaking strengths of the members. This thicknesses are such that the burst strengths of the members are greater than the stresses induced by the gas pressure contained in the bottle.

FIGS. 22 and 23 show operation of mechanism 210 incorporating the embodiment of the gas seal shown in FIG. 21. Referring to FIGS. 22 and 23, upon occurrence of a crash event, the igniter 66 is activated by a signal received from a crash sensor or accelerometer (not shown). When the igniter is fired, a cavity 101 bounded by the extension flange 823 a, the rupturable portion 822, the extension 823 and the housing bore is pressurized. Pressure generated by activation of the initiator acts on extension flange 823 a, applying a load on the flange in the direction of arrow “A” (substantially parallel with axis L″) (see FIG. 22). This force induces an axial tensile load in member rupturable portion 822.

The combination of the stress induced by the bottle gas pressure and the stress induced by the axial load on the flange exceeds the break strength of rupturable portion 822. The rupturable portion fractures along the stress riser. The center portion of the rupturable portion, along with the extension and flange, is pushed down the housing bore by the gas pressure in the bottle, thereby releasing the gas from the bottle.

Pressurized fluid within bottle 18 then flows through rupturable portion 822 and through housing 12, into diffuser 44, and out of the diffuser through orifices 54 and into an airbag or other inflatable element (not shown). A filter (not shown) positioned in diffuser 44 traps by-products of initiator activation, portions of the member, or other debris within the diffuser to prevent their entry into the airbag.

The burst strength of the rupturable portion 822 is greater than the stress induced by the compressed gas in the bottle, but less than the combined stress resulting from the compressed gas and the forces on the extension flange produced by activation of the igniter. The burst strength of the ruptuable portion is also less than the pressure inside the bottle needed to rupture the bottle. This provides a safe gas relief mechanism for over-pressurization situations caused by, for example, a fire external to the gas bottle.

Referring to FIG. 24, an inflator or gas generating system 8 including an embodiment of the gas seal described herein may be incorporated into an airbag system 200. Airbag system 200 includes at least one airbag 202 and an inflator 8 coupled to airbag 202 so as to enable fluid communication with an interior of the airbag. Airbag system 200 may also incorporate (or be in communication with) a crash event sensor 210 including a known crash sensor algorithm that signals actuation of airbag system 200 via, for example, activation of igniter 66 in the event of a collision.

Referring again to FIG. 24, an embodiment of the inflator or an airbag system including an embodiment of the inflator may be incorporated into a broader, more comprehensive vehicle occupant restraint system 180 including additional elements such as a safety belt assembly 150, as seen in FIG. 24. Safety belt assembly 150 includes a safety belt housing 152 and a safety belt 160 in accordance with the present invention extending from housing 152. A safety belt retractor mechanism 154 (for example, a spring-loaded mechanism) may be coupled to an end portion 153 of the belt. In addition, a safety belt pretensioner 156 may be coupled to belt retractor mechanism 154 to actuate the retractor mechanism in the event of a collision. Typical seat belt retractor mechanisms which may be used in conjunction with the safety belt embodiments of the present invention are described in U.S. Pat. Nos. 5,743,480, 5,553,803, 5,667,161, 5,451,008, 4,558,832 and 4,597,546, incorporated herein by reference. Illustrative examples of typical pretensioners with which the safety belt embodiments of the present invention may be combined are described in U.S. Pat. Nos. 6,505,790 and 6,419,177, incorporated herein by reference.

Safety belt system 150 may incorporate (or be in communication with) a crash event sensor 158 (for example, an inertia sensor or an accelerometer) including a known crash sensor algorithm that signals actuation of belt pretensioner 156 via, for example, activation of a pyrotechnic igniter (not shown) incorporated into the pretensioner. U.S. Pat. Nos. 6,505,790 and 6,419,177, previously incorporated herein by reference, provide illustrative examples of pretensioners actuated in such a manner.

It will be understood that the foregoing description of the present invention is for illustrative purposes only, and that the various structural and operational features herein disclosed are susceptible to a number of modifications, none of which departs from the spirit and scope of the present invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined only by the appended claims and their equivalents. 

1. A gas seal for containing a pressurized fluid in a container, the gas seal comprising: a rupturable portion having a stress riser formed therein; and an extension coupled to the rupturable portion proximate the stress riser such that a predetermined minimum force applied to the extension is transferred to the stress riser to produce a rupture of the rupturable portion.
 2. The gas seal of claim 1 wherein at least one stress riser is formed along a first surface thereof.
 3. The gas seal of claim 2 wherein the extension is coupled to the rupturable portion along a second surface of the rupturable portion different from the first surface.
 4. A mechanism for releasably containing pressurized fluid in a container, the mechanism comprising: a housing coupled to the container; a gas seal in accordance with claim 1 mounted in the housing in fluid communication with the pressurized fluid; and a mechanism for generating a predetermined minimum force for acting on the extension to produce a rupture of the gas seal.
 5. An inflator including a gas seal in accordance with claim
 1. 6. A gas generating system including a gas seal in accordance with claim
 1. 7. A vehicle occupant protection system including a gas seal in accordance with claim
 1. 8. The mechanism of claim 4 wherein the rupturable portion is directly attached to the housing, and wherein at least one stress riser is formed along a first surface of the rupturable portion.
 9. The gas seal of claim 1 wherein the extension does not define a cavity therein. 